In a magnetic memory, e.g., a magnetic random access memory (MRAM), a magnetoresistance element is used as a magnetic memory cell that magnetically stores data. A typical magnetoresistance element has a magnetic tunnel junction (MTJ) where a tunnel barrier layer is interposed between two magnetic layers.
In some magnetic memory cells, the upper one of two magnetic layers covers only a part of a tunnel barrier layer, that is, the upper magnetic layer is formed into an island shape.
The formation of a magnetic memory cell having such a structure is disadvantageous because etching of an upper magnetic layer to be formed into an island shape is actually difficult to stop right on the surface of a tunnel barrier layer. For example, in order to prevent a magnetic layer from remaining on the tunnel barrier layer, over-etching is necessary. However, over-etching may form a trench penetrating the tunnel barrier layer, causing a short circuit in the magnetic memory cell.
Furthermore, the lower magnetic layer is only covered with the thin tunnel barrier layer, particularly in the final step of etching of the magnetic layer, causing plasma damage to the tunnel barrier layer and the lower magnetic layer. Therefore, the characteristics of the lower magnetic layer may deteriorate.